list.3: Add details

list.3: NAME: Add description
list.3: DESCRIPTION: Add short description
list.3: SEE ALSO: Add insque(3) and queue(3)
list.3: BUGS: Note LIST_FOREACH() limitations
list.3: RETURN VALUE: Add details about the return value of those macros that "return" a value

Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man3/list.3

@@ -48,6 +48,7 @@ LIST_NEXT,
 LIST_PREV,
 LIST_REMOVE
 .\"LIST_SWAP
+\- implementation of a doubly-linked list
 .SH SYNOPSIS
 .nf
 .B #include <sys/queue.h>
@@ -87,6 +88,8 @@ LIST_REMOVE
 .\".BI "void LIST_SWAP(LIST_HEAD *" head1 ", LIST_HEAD *" head2 ", TYPE, LIST_ENTRY " NAME ");"
 .fi
 .SH DESCRIPTION
+These macros define and operate on doubly-linked lists.
+.PP
 In the macro definitions,
 .I TYPE
 is the name of a user defined structure,
@@ -253,11 +256,39 @@ from the list.
 .\" and
 .\" .IR head2 .
 .SH RETURN VALUE
+.BR LIST_EMPTY ()
+returns non-zero if the list is empty,
+and zero if the list contains at least one entry.
+.PP
+.BR LIST_FIRST (),
+and
+.BR LIST_NEXT ()
+return a pointer to the first or next
+.I LIST_ENTRY
+structre, respectively.
+.PP
+.BR LIST_HEAD_INITIALIZER ()
+returns an initializer that can be assigned to the list
+.IR head .
 .SH CONFORMING TO
 Not in POSIX.1, POSIX.1-2001 or POSIX.1-2008.
 Present on the BSDs
 (LIST macros first appeared in 4.4BSD).
 .SH BUGS
+The macro
+.BR LIST_FOREACH ()
+doesn't allow
+.I var
+to be removed or freed within the loop,
+as it would interfere with the traversal.
+The macro
+.BR LIST_FOREACH_SAFE (),
+which is not present in glibc,
+solves this bug by
+allowing to both remove
+.I var
+as well as free it from within the loop safely
+without interfering with the traversal.
 .SH EXAMPLES
 .EX
 #include <stddef.h>
@@ -312,3 +343,5 @@ main(void)
 }
 .EE
 .SH SEE ALSO
+.BR insque (3),
+.BR queue (3)